Japanese Laid-open Patent Publication No. 2008-89886 discloses an image projection display apparatus such as a projector, etc., that projects an image on a projection surface such as a screen, etc., according to an image signal input from an external device connected thereto such as a PC (Personal Computer), a USB (Universal Serial Bus) memory, etc., in order to display information for a plurality of persons at meetings, lectures, presentations, etc.
When a user uses such an image projection display apparatus, the user needs to connect the external device to the image projection display apparatus and perform an operation for turning on the image projection display apparatus. Thus, when a user uses such an image projection display apparatus, there is a problem that the user feels inconvenience because the user needs to separately perform the operation for connecting the external device to the image projection display and the operation for turning on the image projection display apparatus. It is noted that such a problem may occur not only in the image projection display apparatus such as a projector, etc., but also in another image output apparatus such as a television receiver, a PC, a digital camera, a video camera, a display panel, etc.